(Adds Gazprom comment) WARSAW, July 2 (Reuters) - Gas flows from Russia’s Gazprom via Ukraine to Poland were back to normal after falling 20 percent between Thursday and Friday, Polish gas pipeline operator Gaz-System said on Saturday. Gaz-System spokesman Tomasz Pietrasienski said the operator had received no explanation from Gazprom or from Ukraine’s Ukrtransgaz. Gazprom said it had no comment.